Fly ash is a byproduct of burning pulverized coal in electric power generating plants. It can be a pollutant when carried in the exhaust gases from the plant chimneys or stored at large external containment sites, but collected fly ash may be reused to make cement, bricks, roads and bridges. Georgia Tech School of Economics Ph.D. student Archana Ghodeswar investigated whether promoting the reuse of one type of solid waste for a particular industry might lead to an unintended increase in the generation of other wastes. Her study, co-authored with her Ph.D. advisor, Associate Professor Matthew E. Oliver, was published in the March 2022 issue of Energy Policy. It is titled, “Trading one Waste for Another? Unintended Consequences of fly ash Reuse in the Indian Electric Power Sector.”
In India, fly ash is required by law to be used as a substitute input in other industries. To study the consequences of reuse, Ghodeswar and Oliver analyzed data from 196 Indian power plants across 18 states from 2011 to 2017. They write, “To our knowledge ours is the first study to aggregate these data to address a specific environmental policy question of this nature.”
The research shows that greater reuse of fly ash per kilowatt hour of plant output leads to greater coal use, the use of lower quality coal for combustion, and greater carbon dioxide emissions per kWh of output. In other words, while reducing the environmental and health impacts of fly ash stored at containment sites (fly ash contains heavy metals including lead, mercury, and cadmium, which, when inhaled or ingested, can increase the risk of cancer and other diseases), it also reduces the costs to plants of containing and storing fly ash. As a result, plants are burning dirtier coal and emitting more CO2, worsening air pollution and exacerbating climate change.
How much does the current fly ash reuse policy increase CO2 emissions? Ghodeswar and Oliver note, “Holding plant output constant, our point estimates suggest a one-percent increase in use of a plant’s fly ash waste (measured annually) results in an increase of 972 metric tons of CO2 emissions at a social cost of over $80,000 per year.”
The importance of the study, Ghodeswar and Oliver argue, is that this practice should be better understood if industries and policy makers are to gain a complete accounting of the net economic and environmental benefits thereof. A waste reuse policy targeting a single type of waste in an industry that produces multiple waste flows may simply lead to trading one waste flow for another, thereby offsetting some of the intended environmental and economic efficiency gains.
The article was published in Energy Policy in March 2022. Read it online: https://doi.org/10.1016/j.enpol.2022.112940